Device for cleaning of flue gas

ABSTRACT

The invention pertains to a device for cleaning flue gas, with a container ( 31 ) to which raw gas and an adsorbant/absorbant for cleaning of the raw gas can be supplied via at least one supply opening ( 33 ) and from which the cleaned gas can be removed via at least one outlet opening ( 35 ), whereby moveable built-in parts ( 39 ) are located in the container ( 31 ), whereby the moveable built-in parts ( 39 ) have flexible swirling elements ( 43 ).

BACKGROUND OF THE INVENTION

The invention pertains to a device for the cleaning of flue gas and moreparticularly, to such a device which prevents material deposits therein.

For cleaning of flue gas, for example, for cleaning of exhaust gasesfrom incineration systems, at present mostly wet methods, semidrymethods and dry methods are being used. In this case, wet methods andsemidry methods, as a rule, have higher cleaning efficiency than drymethods. However, wet or semidry methods require a greater expense forthe inlet, outlet and reprocessing of the adsorbant/absorbant employedfor cleaning of the raw gas. In addition, in the container in which theadded adsorbant/absorbant causes the absorption or adsorption of thepollutants, there are extremely aggressive acids which attack the insidewall of the container or built-in parts located therein. The watersejected with salts from the scrubber, must be treated in an effluentprocessing system, which is associated with a considerable expense whichhas an effect, in particular, on smaller flue gas cleaning systems.

Therefore, various methods were proposed to improve the cleaningefficiency of dry flue gas cleaning methods. For example, it isdisclosed in EP-A-0 104 335 that the reaction between the pollutantscontained in the raw gas and the adsorbant/absorbant can be improvedwhen additional water is added. This takes place in such a manner thatin a first step, dry, powdery reaction agent is blown in and in a secondstep, pure water or an aqueous solution or suspension or a reactionmedium is sprayed in. Due to the water added in the second step, areactivation of particles of the reaction medium can be achieved. Due tothe addition of water, the reaction medium can be used more efficiently.

The disadvantage in this case is that the added quantity of water mustbe kept as small as possible so that even at relatively low initial ofthe exhaust, the dew point temperature will be maintained. If this isnot observed, then there will be damage to the system due to the formingof aggressive, aqueous acids.

Furthermore from EP-A-0 029 564 it is known that due to an intensivemixing of the raw gas with the added, dry adsorbant/absorbant, anincrease in the relative speed between the gas and theadsorbant/absorbant particles, and thus an improvement in the reactionrate or of the cleaning efficiency can be achieved. In this regard it isproposed in EP-A-0 029 564 to allow sound to influence the reactants.

From DE-A-32 32 080 it is known that through partial, external return ofthe adsorbant/absorbant or of the deposited solids, an improvement inutilization of the adsorbant/absorbant and thus ultimately a savings inadsorbant/absorbant can be achieved.

To improve the cleaning efficiency, in EP-B-0 203 430 a method or adevice for cleaning of flue gas is proposed, whereby the ratio of thedwell time of an adsorbant/absorbant supplied to the reactor, to thedwell time of the flue gas in the reactor, is controlled and/orregulated in that built-in parts are provided in the reactor which movewith respect to the reactor container, for example, in the form of arotating worm. This worm can be driven at a speed of about 0.5-120 rpm,whereby the adsorbant/absorbant is stored partly on the surface of theworm gear; however, it is constantly swirled up by the flue gases to becleaned, or by additionally injected compressed air. Thus the dwell timeof the heavier adsorbant/absorbant particles can be controlled orregulated relative to the dwell time of the gas in the reactor.

However, the disadvantage of this device or of this method, is that withincreasing operating time of the reactor, a hard layer forms on both theinternal wall of the container and also on the surface of the movingbuilt-in parts; this layer forms due to the solids located in thereactor. This extremely hard and tough layer can practically only beremoved by using mining tools.

Operating experiences with the aforementioned devices or methods haveshown that a uniform atomizing pattern of the sprayed water and auniform distribution of the solids with respect to the flue gas quantitycannot be attained. Due to the resultant irregular and ineffectivemixing of flue gas and adsorbant/absorbant, it is unavoidable that wetzones lead to baked-on deposits and dry zones have unsatisfactoryabsorption.

SUMMARY OF THE INVENTION.

It is an object of the present invention is to create a device for thecleaning of flue gas, in particular for dry cleaning of flue gas, whichhas a high cleaning efficiency and in which adverse effects on operationdue to deposits on the inner wall of the container or on moving partsare prevented.

The invention is based on our finding that the presence of flexibleturbulence elements, which are surrounded by the moving built-in parts,inherently prevent, or greatly reduce, the formation of interferinglayers and then due to a change in shape of the flexible swirlingelements, said layers can be easily removed.

Furthermore, any layer perhaps forming on the inner wall of thecontainer can never interfere so much with the operation of the deviceso that a movement of the moving built-in parts will be impacted to asignificant extent, as is the case, for example, in the device accordingto EP-B-0 203 430, when the rotating worm comes into contact with alayer forming at the inner wall of the container.

The production of deposition layers on the flexible turbulence elementscan be prevented, for example, by providing at certain time intervals achange in the motion speed of the turbulence elements, so that the shapeof the flexible elements will change and thus any already produced, thindeposition layers will blasted off.

In the preferred embodiment of the invention, the flexible turbulenceelements are designed as chains or cables which are located at one orseveral rotating, driven shafts. Thus the attained advantage is amechanically simple and low-cost design, whereby in particular theformation of the turbulence elements as chains will mean that in theevent of a change in the direction of rotation or of the speed ofrotation, a change in the position of the chain links will occur withrespect to each other and with respect to the shaft, so that any alreadyproduced deposition layers will be blasted off or removed by abrasion.

In addition, the advantage is obtained that deposition layers producedon the inner wall of the container will again be knocked off by thechain links, as soon as these layers have become so thick that they comeinto contact with the chain ends.

Thus the invention offers the advantage of a self-actuated cleaning ofboth the flexible turbulence elements and also of the inside wall of thecontainer.

The rotation of the flexible turbulence elements takes place at such aspeed that due to the resulting swirling of the rawgas-adsorbant/absorbant mixture, the reaction speed and thus the degreeof cleaning will be improved due to the resulting high relative speedsbetween the adsorbant/absorbant particles and the raw gas. In contrastto the rigidly moved built-in parts according to EP-B-0 203 430, theflexible turbulence elements of the device according to this inventionare used in the first place, to achieve a sufficient swirling of the rawgas adsorbant/absorbant mixture. Of course, due to the correspondingselection of the rotation speed of the flexible turbulence elements andof the thereby resulting lengthening of the path of theadsorbant/absorbant particles in the raw gas to be cleaned, the ratio ofdwell time of the adsorbant/absorbant to the dwell time of the gas inthe reactor will also be controlled within certain limits.

Furthermore, the advantage is attained of a smaller pressure differencebetween gas inlet side and gas outlet side of the container, since nofixed built-in parts of any kind are necessary which will result in aninherent pressure drop.

Furthermore, due to the use of flexible turbulence elements, a largeloading of the flue gas with adsorbant/absorbant is possible, since dueto a high rotation speed or motion speed of the turbulence elements, ahigh degree of swirling is attained and a formation of deposition layerswithin the container need not be feared. Due to the high throughput ofdust-like solids, a large loading with returned adsorbant/absorbant(i.e. adsorbant/absorbant with only partly adsorptive or absorptiveproperties) will occur, whereby the stochiometric ratio of the stillactive part of the adsorbant/absorbant to the quantity of the substancesto be adsorbed or absorbed, can be near a value of one due to the highlevel of swirling, preferably in a range between 1.0-1.5. Thus we attainthe advantage of an optimum utilization of the adsorbant/absorbant sinceit can be kept within the cycle for a relatively long time.

Due to the high speeds of rotation or movement of the flexibleturbulence elements, in addition to the abrasion caused by the impactingof adsorbant/absorbant particles with each other, there is also ablasting of larger adsorbant/absorbant particles, in addition to therelease of adsorbant/absorbant particles from surface layers inactivewith respect to the desired adsorption or absorption. Thus thegeneration of new, active surfaces is possible.

Finally, with the invented device we have the additional advantage of aneasy dismounting of the moveable built-in parts, since, for example, theshafts can be attached to the container by means of small diameterflanges, so that after dismounting of a flange, the shaft plus theflexible turbulence elements can be removed. Due to the flexibility ofthe turbulence elements, only an opening of relatively small size isneeded for this and thus a flange of small diameter is required.

Finally, due to the absence of rigidly moving built-in parts, we havethe advantage of a good accessibility of or access to the container whenit is stopped, since the flexible built-in parts hang downward due tothe action of gravity and leave enough space for a good accessibility oraccess. Repairs within the container or a replacement of the flexibleelements are thus possible in a simple manner.

Since during a shutdown of the system, the flexible turbulence elementscannot block the passage of the device for the raw gas, the result is,furthermore, an operating dependability even when the turbulenceelements are stopped, even though they are at reduced efficiency.

The formation of the flexible turbulence elements as chains or cablesleads to the advantage of low-cost replacement parts.

In one embodiment of the invention, the flexible turbulence elements arearranged along a helical line along the perimeter of one or more shafts.Thus we have the advantage of a flow component produced upon rotation ofthe shaft and moving to a certain extent in the conveyance direction ofthe worm. Of course, several sectors of these screws can be attached toone shaft whose conveyance direction can also be opposing.

In the preferred embodiment of the invention, the flexible turbulenceelements are organized into several groups on one or more shafts, eachin an axial direction of the shafts, whereby preferably the groups ofeach shaft are located between two planes perpendicular to the shaftseach in the same axial sectors. If the shafts are positioned parallel tothe longitudinal axis of the container, then in the direction of the gasflow, this factor will thereby produce zones of extremely turbulentswirling and calmer zones, so that extremely high relative speeds occurbetween the adsorbant/absorbant particles and the flue gas, inparticular at the boundary interfaces.

The container in the device according to this invention can be employedboth prone or also standing, so that the device can be very flexiblyadapted to the existing space requirement.

In a preferred embodiment of the invention, the container has a wallwhose inside is cylindrically designed or consists of several partlycylindrical regions. In this case, each shaft is provided essentially inthe axis of the cylinder and/or of a partial cylinder. Thus we have theadvantage that in the case of a corresponding design of the length ofthe turbulence elements with suitable selection of the speed of theshaft or of the shafts, layers building up at the inner wall of thecontainer cannot continue to build up beyond a preset thickness, sincethe ends of the rotating turbulence elements will cause a diminution ofthe layers. Thus a self-cleaning effect can be achieved.

If the wall is constructed of several partly cylindrical regions and ifseveral shafts are provided with turbulence elements, then we have animproved swirling of the gas adsorbant/absorbant mixture. Due to theformation of the inner wall in the shape of several partly cylindricalregions, in contrast to a purely cylindrical structure, a quasi-laminarflow of the mixture as a kind of rotating (screw-shaped) motion will beavoided.

But of course, any other-shaped flow control elements can be provided atthe inside wall of the container, which contribute, due to a continuingchange in local flow velocity, to a better swirling of the gasadsorbant/absorbant mixture.

To improve the swirling, an even number of shafts with turbulenceelements can be provided, whereby mutually neighboring shafts can bedriven oppositely. For self-cleaning of the turbulence elements, therotational velocity can be changed after a previously defined time, forexample, the speed can be reduced and then increased again. In the sameway, after a previously determined time, the direction of rotation ofthe shafts can be reversed.

According to another embodiment of the device according to thisinvention, the container can be set up in a prone position, i.e., thelongitudinal axis of the container can run essentially horizontally, andthe shafts can be positioned perpendicular to the longitudinal axis ofthe container. In this embodiment, the container can have an essentiallyrectangular cross section, whereby the walls of the container locatedparallel to the shafts have inner sides which consist of several partlycylindrical regions. Each shaft in this case is provided preferablyessentially in the axis of a cylinder part. In this case, in ananalogous manner, the advantages discussed above will be obtained. Theshafts in this embodiment can, of course, be arranged in the verticaland/or horizontal directions.

In order to prevent, or allow only very little swirling of the mixtureat the insides of the walls of the container perpendicular to theshafts, flow control elements can be provided at these insides, orregions of the insides can be shaped accordingly. In a simpleembodiment, these flow control elements can, in turn, be formed ascircle-cylindrical walls which are arranged coaxial to the shafts.

These embodiments with shafts arranged perpendicular to the longitudinalaxis of the container (whether for vertical or horizontal arrangement ofthe container) offer the added advantage that a modular structure of thecontainer is possible. Depending on the desired cleaning power ordesired purity of the cleaned gas, a required number of modules can thusbe combined into one container. This will significantly reduce the costsfor planning and building of a flue gas cleaning system. Furthermore,subsequent changes to an existing system will be possible by simple andlow-cost means.

In the preferred embodiment of the invention, at least one inlet openingis provided each for the raw gas and the adsorbant/absorbant. But ofcourse, the mixing of the adsorbant/absorbant with the raw gas can alsotake place at a location connected by an inlet to the container.

In the embodiment of the invention with a standing container, thecleaning of the gas can occur, of course, in a uni-flow or counterflowprinciple, whereby the flow direction of the gas can run either frombottom or top, or vice-versa. The inlet openings for theadsorbant/absorbant and the inlet or outlet of the gas are in this caselocated in the appropriate manner.

In the embodiment of the invention with prone container, essentiallyonly the cleaning in a uni-flow principle will come into consideration,since due to the gas flow, a conveyance of the adsorbant/absorbantparticles will occur.

In the preferred embodiment of the invention, in a bottom region of thecontainer there is a collection device for the adsorbant/absorbant,which has preferably a conveyor which extends across the entire lengthof the bottom region of the container or across a bottom regionneighboring the gas outlet side. If necessary, the conveyor can bepartly covered by means of one or several pieces of covering sheetmetal.

The collection device is thus preferably designed so that apredetermined part of the adsorbant/absorbant can be supplied to thecontainer in the form of a cycle, whereby the adsorbant/absorbantlocated in the collection shaft is used to maintain the pressuredifference between the gas inlet side and the gas outlet side of thecontainer. This, then, will prevent gas from moving via the externalinlet path of the adsorbant/absorbant and the collection device in thedirect vicinity of the gas-removal opening into the container, withouthaving to pass through the correct “cleaning path.”

The inlet opening of an adsorbant/absorbant inlet device is provided atthe container of the device according to the invention. Through thisadsorbant/absorbant inlet device the necessary quantity ofadsorbant/absorbant is brought into the container and that portion ofthe adsorbant/absorbant which is ultimately removed from the collectiondevice for disposal, is replaced in the form of fresh, unspentadsorbant/absorbant.

At the same time, the adsorbant/absorbant inlet device can be composedof a device for admixing water up to a predetermined moisture content,so that a reactivation of the adsorbant/absorbant dried as a result ofthe last passage through the container will be achieved. In this case,the result can be a reactivation of the already reacted surface of theadsorbant/absorbant particles, and secondly, the water from theadsorbant/absorbant particles will be sucked into the interior of theparticles due to capillary action, so that as a result of the suddenheating after inlet into the interior of the container, there will be asudden evaporation of the water. Thus the particles will be blown apart(“popcorn effect”) and thus an enlargement of the adsorbing or absorbingsurface area will be achieved.

Due to the addition of water directly to the adsorbant/absorbant, beforeit is introduced into the interior of the container, the additionaladvantage is attained that a relatively high moisture quantity can besupplied into the container, without an outwardly noticeable materialmoisture occurring. The macroscopic structure of the adsorbant/absorbantpresent in the cycle remains unchanged, dry and finely powdered, i.e.,the adsorbant/absorbant remains swirlable just like dry dust. Of course,the same is also true for the produced, aggressive, aqueous acids. Inthis manner we can mostly prevent the interior walls of the containerand/or the moving built-in parts from being attacked by the produced,aggressive substances. Of course, it is quite possible that layers ofthe adsorbant/absorbant can settle on the flexible turbulence elementsin the turbulent region. However, this is not a disadvantage due to theformation of the flexible, turbulence elements.

This method of admixing of water into the adsorbant/absorbant before itsinlet into the container and the necessary devices for this, can, ofcourse, be used in combination with known, dry flue gas cleaning methodsand devices. Of course, the advantage of a high cleaning efficiency dueto the high and effective throughput of adsorbant/absorbant possiblewith the invented container, cannot be achieved in association with theknown containers.

If calcium hydroxide (Ca(OH)₂) is used as adsorbant/absorbant, theninstead of a device for admixing of water, a device for admixing milk oflime can be provided. In other words, the necessary addition of freshadsorbant/absorbant in the form of dry calcium hydroxide and theseparate addition of water can be replaced in that milk of lime can beadded in a single addition step. Thus the expense for theadsorbant/absorbant inlet device will be reduced, and secondly, weobtain the added advantage that the milk of lime for addition can beproduced from calcium oxide (CaO) and water. Therefore, it is necessaryto deliver to the filter plant only calcium oxide (it is assumed, here,that water will be available on site anyway), whereby the requiredquantity of calcium oxide is far less than the comparable, neededquantity of calcium hydroxide.

In this case, to start up the plant, it is necessary that the collectionshaft of the collection device be filled with dust-likeadsorbant/absorbant before the initial operation.

Due to the special formation of the moving built-in parts as flexiblebuilt-in parts which makes possible a high throughput ofadsorbant/absorbant, in a device according to this invention, alsocalcium silicate hydrate (CaSiOH) up to a grain size of 5 mm and morecan be used as adsorbant/absorbant. Calcium silicate hydrateprecipitates in this form as waste in the production of aerated-concreteand thus represents a very low-cost adsorbant/absorbant. Due to the thusoccurring, relatively large particles, their use with known apparatuseswas not possible or was not profitable due to the necessary processingof the calcium silicate hydrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in greater detail below based on thedesign example presented in the figures. The figures show:

FIG. 1: a schematic representation of the entire system for cleaning offlue gas;

FIGS. 2 a, 2 b: a representation of a first embodiment of the deviceaccording to this invention, shown in cross section (FIG. 2 alongitudinal cross section; FIG. 2 b cross section through thecontainer);

FIG. 3 a partial cross section through the adsorbant/absorbantcollection device according to line I—I in FIG. 2 a;

FIGS. 4 a, 4 b: an additional embodiment of the invention with pronecontainer in two longitudinal cross sections shown in two mutuallyperpendicular planes;

FIGS. 5 a, 5 b: an additional embodiment of the invention with pronecontainer in the representation according to FIGS. 4 a, 4 b; and

FIGS. 6 a, 6 b; an additional, simplified embodiment of the inventionwith prone container in the representation according to FIGS. 4 a, 4 b,5 a and 5 b.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The overall system illustrated in FIG. 1 for cleaning of flue gasconsists essentially of a precooler 1, and the raw gas to be cleaned issent to it through a valve 3 in the direction of the arrow and of theactual device 5 for cleaning of the flue gas, with a solids separator 7outlet connected to it. The cleaned flue gas is then output through asmokestack 9. Of course, due to a parallel circuitry of several devices5, the cleaning power can also be increased, or the cleaning of thegases can be improved by a series circuiting of several devices 5.

The path of the gas through the system in normal operation is indicatedin FIG. 1 by the thick, solid lines and arrows.

The thin, solid lines represent paths which ensure the operationaldependability in case of malfunction of one or more components. Forexample, the line 11 and the associated valve 13 pertain to an emergencybypass, with which the entire system can be bridged and the raw gas canbe sent directly to the stack 9.

By means of the line 15 and the associated valve 17, in association withan appropriate control of the valves 19 and 21, it is possible to bridgethe device 5.

Finally, by means of the line 23 and an associated driver of the valves25, 27 and 29, it is possible to bridge the solids separator 7.

The device 5, which is illustrated in FIG. 2 a, is composed of acontainer 31 and the raw gas is supplied to it in the direction of thearrow through an inlet opening 33. The cleaned, raw gas is sent throughan outlet opening 35 in the lower region of the container 31 and to thesolids separator 7 (FIG. 1), which can be designed, for example, as acloth filter. Dry or quasi-dry dust-like or powdered adsorbant/absorbantcan be supplied to the container 31 through an adsorbant/absorbantdevice 37.

Since the adsorption and/or absorption of harmful pollutants in the rawgas is improved by the adsorbant/absorbant particles, when they have acertain moisture, in the adsorbant/absorbant supply device 37 underadmixing of the adsorbant/absorbant, water is added until a predefinedmoisture content is achieved. Of course, this can take placeindependently in the form of a closed control circuit, whereby themoisture content can be selected depending on certain parameters, forexample, the temperature of the supplied raw gas. In this manner, themoisture content of the adsorbant/absorbant before the inlet into theinterior of the container 31 can be increased, for example, up to thelimit of the presence of a dust-like structure. However, theadsorbant/absorbant in this case is still in dust-like or powder form,so that as before, a large, active surface area is available for thecleaning.

Since a high relative speed between the adsorbant/absorbant particlesand the raw gas is desirable to increase the efficiency, in thelongitudinal axis of the container 31 there are several (in theillustrated example, four) shafts 39 which run parallel to thelongitudinal axis of the container. The shafts are rotated by means ofdriven electromotors 41 which are provided at the top side of thecontainer 31.

To swirl up the gas adsorbant/absorbant mixture, chains 43 are providedon the shafts 39 inside the container. These chains hang down due togravity when the shafts are stopped, and extend due to the action ofcentrifugal force, outward when the shafts rotate. Of course, instead ofchains, any other kind of flexible turbulence elements can be used, forexample, cables. However, chains offer the advantage that due to theleads in the chain links, a more intensive swirling can be obtained.Also, smaller, rigid or flexible elements can be attached to theflexible turbulence elements (in a manner not illustrated) to increasethe air resistance.

As illustrated in FIGS. 2 a, 2 b, the container 31 can have a wall 31 awhose inside wall has several partly cylindrical regions 31 b. The fourshafts are then arranged, as illustrated in FIG. 2 b, preferably in sucha manner that they reside in the axis of the partly cylindrical regions31 b.

Firstly, this will ensure that the gas, as a result of the swirling bythe turbulence elements 43 of each shaft, will be directed from theinner wall of the regions 31 b back in the direction of the containermiddle. To improve the swirling, neighboring shafts 39 can be drivenwith an opposing sense of rotation, as illustrated in FIG. 2 b. Theturbulence elements 43 designed as chains are then selected preferablyto be long enough so that their outer ends describe an outer circle—at apredefined speed—whose diameter is only slightly smaller than the innerdiameter of the partly cylindrical regions 31 b. In the course of theoperation of the device, if adsorbant/absorbant layers build up on theinner wall of the container 31, then these layers will be knocked off bythe chain ends as soon as the layer thickness exceeds a particularvalue. In each case, compared to the use of rigid turbulence elements,even given larger layer thicknesses, the motive power needed formovement of the shafts 39 remains essentially unchanged.

In order to prevent the build-up of thicker layers on the turbulenceelements 43, as already mentioned, the direction of rotation of eachshaft 39 can be reversed at certain time intervals, or the speed ofrotation can be changed. Thus, a change in shape of the flexibleturbulence elements 43 will be obtained, so that the potentiallydeposited layers will be blasted off.

As indicated in FIG. 2 b, the shafts 39 can have a synchronizedoperation, with regard to their rotational motion, so that the chains 43do not beat against each other in the middle of the container. Forcleaning purposes, this synchronization can also be ceased for a shorttime, so that the chains will clean each other by means of mutualimpacts.

In the axial direction of the shafts 39, the chains can be uniformlydistributed, for example, so that to avoid imbalances or flexure of theshafts, a symmetrical arrangement of chains in a plane perpendicular tothe shaft is preferred. As illustrated in FIG. 2 b, for example, fourchains can be provided in one plane. The chains 43 can also havedifferent lengths in order to achieve the desired swirling effects.

As illustrated in FIG. 2 a, the chains can be arranged in groups in theaxial direction, whereby zones of large turbulence will alternate withcalmer zones. In particular in the transition layers, high relativespeeds will be produced between the adsorbant/absorbant particles andthe gas.

At the bottom end of the container 31 there is a collection device 45for the adsorbant/absorbant, which comprises a conveyance device 47—asclearly indicated in FIG. 3—which supplies the adsorbant/absorbantcollecting on the conveyor chain 49 (partly laden with pollutants) to acollection shaft 51. The conveyor chain 49 extends preferably across theentire bottom surface of the container 31.

At the bottom end of the collection shaft 51 there is an additionalconveyance device 53, which uses an additional conveyor chain 55 toagain supply the adsorbant/absorbant to the adsorbant/absorbant inletdevice 37. The latter can comprise, for example, a conveyor path 57designed as a bucket conveyor. The dust-like product—which consistsessentially of adsorbant/absorbant—deposited by means of the solidsseparator 7 (FIG. 1), is supplied to the conveyor path 57. Thus anoptimum utilization of the adsorbant/absorbant will result.

Furthermore, the adsorbant/absorbant supply device 37 is composed of aninlet device 58 for fresh material, that is, fresh adsorbant/absorbant.This fresh material supply device can, as shown in FIGS. 1 and 2 a,supply the fresh material to the underside of the conveyor path 57 froman adsorbant/absorbant silo 62 (FIG. 1). But of course, the inlet offresh material can also occur at any location between theadsorbant/absorbant inlet opening and the adsorbant/absorbant collectiondevice 45. The quantity of fresh material supplied to theadsorbant/absorbant already present in the cycle can be controlled orregulated as a function of particular parameters, e.g., the quantity ofpollutants to be adsorbed or absorbed.

In addition, by means of the adsorbant/absorbant supply device 37, waterup to a particular moisture content, can be added to theadsorbant/absorbant already present in the cycle, in the mannerdescribed above.

A fraction of the produced reaction product corresponding to the inletand outlet quantity, is sluiced out of the adsorbant/absorbant cyclefrom the collection shaft 51—as illustrated in FIG. 3—by means of anoutlet device 59, which can be composed of a conveyor worm, forinstance, and then sent to the residual silo 61 (FIG. 1) for disposal.The quantity of adsorbant/absorbant present in the cycle will thus bekept essentially constant.

Due to the adsorbant/absorbant layer present in the collection shaft 51,at the same time it is possible to maintain the pressure differencebetween the inlet opening 33 and the outlet opening 35 for the gas andin this manner to prevent the raw gas from moving via theadsorbant/absorbant inlet device 37 and the collection shaft 51 in thedirection of the outlet opening 35, without having passed through thecorrect cleaning procedure.

The above design of the adsorbant/absorbant supply device 37 and of theadsorbant/absorbant collection device 45 will ensure the desired,high-level adsorbant/absorbant throughput through the container 31. Ofcourse, these elements can also be used with known containers 31.

Viewed as a whole, with regard to a device according to this invention,not only an improvement of the cleaning efficiency with simultaneouslysimple design of the device will result, but rather also an improvementin the utilization of the adsorbant/absorbant due to the reactivation inthe adsorbant/absorbant supply device. Each adsorbant/absorbant particlepasses several times through the container 31 and contributes repeatedlyto a cleaning of the gas. The adsorbant/absorbant thus remains—given anappropriate total quantity of adsorbant/absorbant within the cycle—for arelatively long time in the cycle (two days and more), so that theadditional advantage is obtained that resulting reaction products willbe oxidized by the residual oxygen present in the gas and due to themoisture. For example, calcium sulfite (CaSO₃) present in theadsorbant/absorbant will be oxidized to calcium sulfate (CaSO₄). Thiswill occur right within the adsorbant/absorbant cycle. Anoutlet-connected step for oxidation of the spent adsorbant/absorbantremoved by the outlet device 59 is thus not necessary.

Now let us turn to the additional design example of the inventionpresented in FIG. 4 a and 4 b, where we will discuss solely thedifferences to the design example according to FIGS. 2 and 3. Inparticular, essential parts of the collection device 45 for theadsorbant/absorbant and the adsorbant/absorbant supply device 37 remainin principle unchanged.

As illustrated in FIG. 4 a, the container 31 of the device 5 ispositioned prone, whereby the shafts 39 are positioned perpendicular tothe longitudinal axis of the container in a vertical direction. Thepropulsion of the shafts remains essentially unchanged.

Due to the prone formation of the container 31 there results theadvantage that the bearing of the shafts can be placed outside of thecontainer interior, in particular also at the underside, and thus thebearings are protected against aggressive gases. The inlet opening 33for the raw gas initially expands up to the entire cross section of thecontainer 31, so that a reduction in the rate of flow will be achieved.In this manner, the gases to be cleaned remain within the container 31,which contributes to an increase in the cleaning effect.

The chains 43 provided on the shafts 39 are positioned essentially atequidistant, axial intervals around the shafts and are distributed alongthe perimeter of the shaft, so that an imbalance will be avoided. But ofcourse, in this design as well, in each plane there are several, forexample, four, chains so that in each plane perpendicular to the shaft,an imbalance will be precluded.

As is evident from FIG. 4 b, the inner walls of the container parallelto the shafts 39, are again equipped with partly cylindrical sections 31b′, so that the advantages described above will be obtained.

In order to prevent the formation of calm zones with respect to theswirling, the container interior walls running perpendicular to theshafts can have along these interior walls (as explained in associationwith FIGS. 6 a and 2 b flow control elements (not illustrated) whichprevent an unhindered gas flow in the direction of the gas outletopenings 35.

In the bottom wall of the container 31, in the vicinity of the gasoutlet opening 35, there is a collector device 45 for theadsorbant/absorbant. This device, in turn, is composed of a conveyordevice 47 which extends over the entire width of the container 31.Furthermore, the collection device 45 is unchanged, likewise also theadsorbant/absorbant inlet device 37. For reasons of conciseness, therepresentation of the cycle for the adsorbant/absorbant was omitted.

In this embodiment of the invention, essentially only an operationaccording to the uniflow principle will be possible.

With regard to the device according to FIGS. 4 a and 4 b the suppliedadsorbant/absorbant particles repeatedly settle on the bottom wall andare repeatedly swirled up. Thus the adsorbant/absorbant particles arecarried along by the gas stream in the direction of the gas outletopening 35. Since in the rear region of the container 31, i.e., in theregion of the collection device 45 no more rotating shafts are provided,the adsorbant/absorbant particles mostly settle onto the conveyor chainof the collector device 45. Those particles which are carried along bythe gas stream in the direction of the gas outlet opening 35, willsettle, due to the force of gravity, through the slanting,upward-directed formation of the exhaust channel, in the course of time,onto the lower wall of the outlet channel and will then slide down alongthis wall, due to the relatively great steepness, in the direction ofthe collection device 45. In this manner it will be assured that themajority of the adsorbant/absorbant will get into the collection device45. The fraction of the adsorbant/absorbant, in particular the smalleradsorbant/absorbant particles, carried off by the gas stream through thegas outlet opening in each embodiment, will then be regenerated via thesolids separator 7 (FIG. 1).

The embodiment according to FIGS. 5 a and 5 b differs from theembodiment according to FIGS. 4 a and 4 b solely in that the shafts 39are positioned horizontal and perpendicular to the longitudinal axis ofthe container 31. Thus, the reader is referred to the above description.

As illustrated in FIG. 5 a, the collection device 45 for theadsorbant/absorbant is provided with a longer conveyor chain which isdriven until the adsorbant/absorbant located on the conveyor chain ismoved in the direction of the container end, and from there is conveyedto the underside of the conveyor chain in the direction of thecollection shaft. This will then mean that the concentration of theadsorbant/absorbant particles in the region of the shafts 39, which arelocated above the conveyor chain, is reduced with respect to theadsorbant/absorbant concentration in the front region of the container31. In this manner the fraction of adsorbant/absorbant particles carriedoff by the gas through the gas outlet opening 35 will be reduced.

Due to the horizontal formation of the shafts 39, the chains 43 at lowshaft speed, for example, during stoppage of the device, will wind uparound the shafts so that an unhindered access to the interior region ofthe container 31 is possible. But at a higher rotational velocity, thechains will unwind due to the centrifugal force, so that in this designas well, an optimum swirling of the gas adsorbant/absorbant mixture isassured.

FIGS. 6 a and 6 b show a simplified embodiment of the invention withlikewise prone container 31. Just as in the embodiment according toFIGS. 5 a and 5 b, the shafts 39 are again arranged horizontal andperpendicular to the longitudinal axis of the container 31. But incontrast to this embodiment, only a single row of shafts 39 is provided,whereby the chains are designed only to be long enough so that contactof the chains with each other is prevented. Consequently, asynchronization of the drive units for the shafts 39 can be omitted.Also, as best shown in FIG. 6 b, chains 43 are axially spaced apartalong respective shaft 39 such that the chains are attached to the shaftalong a helical line around the perimeter of the respective shaft.

Whereas the upper wall of the container 31 again has the known partlycylindrical regions, a conveyor chain of the collector device 45 for theadsorbant/absorbant extends over the entire lower inner wall. Asillustrated in FIG. 6 a, this chain can be driven either so that theupper side of the conveyor chain will move in the direction of the gasoutlet opening 35, so that the adsorbant/absorbant will be promotedbetween the underside of the conveyor chain and the container inner wallin the direction of the collector shaft of the device 45. Thus we have arelatively rapid transit of the adsorbant/absorbant, which is repeatedlyswirled up from the upper side of the conveyor chain.

However, the conveyor chain can also be driven oppositely, so that theadsorbant/absorbant which settles onto the conveyor chain is repeatedlymoved in the direction of the gas inlet opening 33. However, the speedof the conveyor chain will then have to be selected as greater than theaverage speed of motion of the adsorbant/absorbant particles in the gasstream. In this driving of the conveyor chain, the dwell time of theadsorbant/absorbant particles in the interior of the container 31 can beincreased.

As illustrated in FIGS. 6 a and 2 b, flow control elements 63 can beprovided below the conveyor chain of the adsorbant/absorbant collectiondevice 45; these flow control elements are located in regions betweenthe outer circular paths of the chains 43 and exert a functioncorresponding to the circular-cylindrical regions 31 b′ of the upperwall.

Furthermore, as indicated by dashed lines in FIG. 6 a and also asevident in FIG. 6 b, additional flow control elements 65 are provided onthe lateral, inside walls of the container 31, which prevent the gaswith little or no swirling, from moving along these paths from the inletopening 33 to the outlet opening 35.

What is claimed is:
 1. A device for cleaning flue gas, the devicecomprising: (a) an elongated container having at least one supplyopening and at least one outlet opening, the at least one supply openingfor receiving raw gas to be cleaned and an adsorbant/absorbant into thecontainer and the least one outlet opening enabling cleaned gas to exitthe container; (b) a plurality of rotating, driven shafts located in thecontainer and extending perpendicular to the longitudinal axis of thecontainer; and (c) each rotating, driven shaft having a plurality offlexible swirling elements connected thereto.
 2. The device according toclaim 1 wherein the flexible swirling elements are chosen from a groupconsisting of chains and cables.
 3. The device according to claim 1wherein the flexible swirling elements connected to at least one shaftare arranged along a helical line at the perimeter of said shaft.
 4. Thedevice according to claim 1 wherein the flexible swirling elements areseparated into groups on at least one shaft, and the groups areseparated in an axial direction on the shaft.
 5. The device according toclaim 4 wherein the groups of flexible swirling elements on said shaftare spaced apart in equal sections between two planes locatedperpendicular to the shaft.
 6. The device according to claim 1 whereinthe longitudinal axis of the container runs essentially vertically. 7.The device according to claim 1 wherein the longitudinal axis of thecontainer runs essentially horizontally.
 8. The device according claim 1wherein the container has an essentially rectangular cross section. 9.The device according to claim 1 further comprising a collection deviceassociated with the container for collecting the adsorbant/absorbant.10. The device according to claim 9 wherein the collection device isprovided at the bottom side of the container and has a verticallongitudinal axis.
 11. The device according to claim 9 wherein thecollection device has a horizontal longitudinal axis and is provided ata bottom region of the container.
 12. The device according to claim 11wherein the collection device includes a conveyor extending over theentire length of the bottom region of the container.
 13. The deviceaccording to claim 11 wherein the collection device includes a conveyorextending over the entire length of a region neighboring a gas-removalend of the container in which the at least one outlet opening issituated.
 14. The device according to claim 9 wherein the collectiondevice conveys the adsorbant/absorbant into a collection shaft fromwhich a predetermined portion of the adsorbant/absorbant can be recycledthrough the container, whereby the adsorbant/absorbant located in thecollection shaft is used to maintain a pressure difference between a gasinlet end of the container in which the at least one supply opening islocated and a gas outlet end of the container in which the at least oneoutlet opening is located.
 15. The device according to claim 14 furthercomprising a removal device associated with the collection shaft, theremoval device for removing a portion of the adsorbant/absorbant fordisposal.
 16. The device according to claim 14 further comprising anadsorbant/absorbant inlet device provided on the container, theadsorbant/absorbant inlet device being connected to the collectionshaft.
 17. The device according to claim 16 further comprising a waterinlet connected to the adsorbant/absorbant inlet device for admixingwater with the adsorbant/absorbant up to a predetermined moisturecontent.
 18. The device according to claim 8 wherein the containerincludes walls extending parallel to the plurality of shafts, andwherein said walls have inside surfaces which consist of partlycylindrical regions, and wherein a different one of the plurality ofshafts is positioned essentially at the axis of each of the partlycylindrical regions.
 19. The device according to claim 8 wherein thecontainer includes walls extending perpendicular to the plurality ofshafts, and further comprising flow control elements positioned on theinside surfaces of the walls extending perpendicular to the plurality ofshafts, the flow control elements extending from the respective wallinwardly into an interior of the container for diverting the flow of thegas and adsorbant/absorbant mixture toward the middle of the container.20. The device according to claim 1 wherein at least one supply openingis provided in the container for the raw gas and at least one supplyopening is provided in the container for the adsorbant/absorbant. 21.The device according to claim 20 wherein the at least one supply openingfor the raw gas, and the at least one supply opening for theadsorbant/absorbant, and also the at least one outlet opening for thecleaned gas, are arranged in axial end regions of the container so thatthe cleaning of the raw gas takes place in a uniflow or counter flowcondition.